Separation apparatus

ABSTRACT

A separation process comprises passing a gas or vapor stream contaminated with an undesired substance or contaminant downwardly through a bed of curled separating media. The undesired substance or contaminant is allowed to separate from the gas or vapor as it passes through the bed. Purified gas or vapor is withdrawn from the bed.

FIELD OF THE INVENTION

THIS INVENTION relates to separation apparatus. It relates also to aseparation process, and to a cooking installation.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided aseparation process, which comprises

passing a gas or vapour stream contaminated with an undesired substanceor contaminant downwardly through a bed of curled separating media;

allowing the undesired substance or contaminant to separate from the gasor vapour as it passes through the bed; and

withdrawing purified gas or vapour from the bed.

The bed may be located in a separation zone having a gas/vapour inletand a gas/vapour outlet, with the bed positioned between the inlet andthe outlet. The gas or vapour stream may enter the separation zone andpass through the bed at a relatively high velocity (V₁), with itsvelocity decreasing to a lower value (V₂) on exiting the bed and priorto passing through the outlet. Thus, typically, V₁ may be between 2 and10 m/s, while V₂ is preferably less than 2 m/s. The ratio of V₁ :V₂ maythus be between 5:1 and 1:1. The Applicant believes that the decreasedvelocity of the gas or vapour stream as it passes through the bed,enhances separation of the contaminant from the gas or vapour.

The process may include allowing excess undesired substance orcontaminant to drip from the separating media, and catching this excessundesired substance or contaminant at the bottom of the separation zone.

The process may also include passing the gas or vapour stream from theseparation zone through a scrubber for removing an undesired substancesuch as ammonia therefrom, and/or passing it through a biological filterfor removal of a substance such as sulphur therefrom, before dischargingthe treated gas or vapour stream to atmosphere.

The gas or vapour stream may be at an elevated temperature at which theundesired substance or contaminant is in condensible vaporized form. Theprocess may then include, prior to passing the contaminated gas orvapour stream through the curled separating media bed, cooling the hotgas or vapour stream immediately ahead of the curled separating mediabed, with condensed contaminant or undesired substance thus separatingfrom the gas or vapour stream as it passes through the bed.

The cooling of the hot contaminated gas or vapour stream may be effectedby directly contacting the hot gas or vapour stream with a coolingmedium. The cooling medium may be at between -30° C. and ambienttemperature, eg at between -15° C. and 10° C.

In one embodiment of the invention, the cooling medium may comprise agas or vapour stream. The process may thus comprise admixing the hot gasor vapour stream with a coolant gas or vapour stream, to form a mixedgas or vapour stream, which is then passed downwardly through the bed ofcurled separating media.

The coolant gas or vapour stream is thus used to control the temperatureof the gas or vapour stream passing through the bed of curled separatingmedia. The process may then include regulating the flow rate of thecoolant gas or vapour stream, in response to the temperature and flowrate of the hot gas or vapour stream, to control the temperature of thecooled mixed gas or vapour stream. Thus, the temperature of the hot gasor vapour stream typically will be in the range 40° C.-180° C., eg from80° C.-100° C., with the desired temperature of the mixed gas or vapourstream typically being 15° C.-60° C., such as between 30° C. and 50° C.,eg about 40° C.; hence, sufficient coolant gas or vapour will beadmixed, by means of the coolant gas or vapour stream, with the hot gasor vapour stream to control the mixed gas or vapour stream temperatureat the desired temperature or within the desired temperature range.

Instead, the cooling medium may comprise a coolant liquid. The processmay then include spraying the coolant liquid into the hot gas or vapourstream. The spraying may be effected continuously or intermittently.

Both the gas or vapour cooling and the liquid cooling may be used, ifdesired. Thus, the mixed gas or vapour stream may then be subjected tothe liquid spraying, if necessary or desired.

The process may also include, when the pressure drop through the mediabed becomes excessive due to contamination of the media and/or solidsbuild-up in the bed, displacing the bed so that the gas or vapour streamenters a different zone of the bed. Thus, the bed may have an entry zoneor portion through which the contaminated gas or vapour stream entersthe bed and an exit zone or portion through which the purified gas orvapour stream leaves the bed, with the zones being located on oppositesides of a rotational axis, and with the displacement of the bed beingthrough 180° and being effected by rotating it about the axis so thatthe entry zone becomes the exit zone and the exit zone becomes the entryzone.

The process may include, in a cleaning cycle, washing the curledseparating media bed after it has been displaced, to clean or regeneratethe media and to improve gas or vapour flow through the bed.

The washing may include spraying hot washing liquid, eg wash water, ontothe bed, while continuing to pass the gas or vapour stream through thebed. The washing liquid may include a washing aid, eg a detergent, toassist in cleaning of the media. The process may include collecting, fora period of time, the washing liquid passing through the bed; recyclingthe washing liquid, ie re-using it for the spraying onto the media bed;and dumping the washing liquid after the period of time, ie at the endof the cleaning cycle.

The contaminated gas or vapour stream may be an off or waste gas streamemanating from a household, commercial or industrial cooker. Thus, thegas or vapour is then air, while the contaminant or undesired substanceis then fat and/or oil. The air may be hot as hereinbefore described, inwhich case the fat and/or oil is present therein in condensiblevaporized form. The coolant gas or vapour stream, when present, may thusbe cooler air, eg atmospheric air or coolant air, not contaminated withsuch fat or oil. The coolant liquid, when present, may be water.

The Applicant has found that, apart from the curled separating mediaacting to remove condensed or liquid contaminants, they also act toremove solid contaminants. Without wishing to be found by theory, theApplicant believes that this may be due to localized cyclone actionstaking place within the bed of curled separating media.

According to a second aspect of the invention, there is provided aseparation apparatus, which comprises

a vessel defining a separation zone;

a contaminated gas/vapour inlet leading into the vessel;

a gas/vapour outlet leading from the vessel;

separating means comprising a bed of curled separating media in theseparation zone, the inlet, the separating means and the outlet arrangedsuch that a contaminated gas or vapour stream entering the separationzone through the inlet passes downwardly through the bed and exits thezone through the outlet, with the curled separating media acting toseparate contaminants from the gas or vapour as the gas or vapour streampasses through the bed.

The vessel may have a base or floor, a roof spaced from the base, and aperipheral wall between the base and the roof. The relative dimensionsof the inlet and the vessel may be such that a reduction in gas orvapour stream velocity as it enters the separation zone, takes place.

In one embodiment of the invention, the inlet may be provided in theroof, with the outlet being provided in the wall. The separation meansmay then include an apertured basket in the vessel below the air inlet,with the separation media contained in the basket as a fixed bed. Abaffle may separate the inlet from the outlet, with the baffle dependingfrom the vessel roof and terminating with clearance from the vesselfloor. Thus, gas or vapour will pass downwardly through the bed ofseparating media, underneath the baffle, and upwardly through the spacebetween the baffle and the vessel wall, to exit through the outlet.

The apparatus may include a contaminant collection zone inside thevessel adjacent the floor such that it is spaced from the bed of curledseparating media. In another embodiment of the invention, the inlet maythen be provided in the wall at a high level, with the outlet beingprovided in the wall and/or in the roof such that it is in communicationwith the space between the bed of curled separating media andcontaminant collection zone.

In a first version of this embodiment of the invention, the floor androof may then be square or rectangular in plan view, with the wall thuscomprising four wall panels connecting the floor and the roof, the inletbeing provided in one wall panel at said high level and the outlet beingprovided in an opposed wall panel at a lower level.

In a second version of this embodiment of the invention, the floor androof may then be square or rectangular in plan view, so that the wallcomprises four wall panels connecting the floor and the roof, with oneof the inlets being provided in each of two opposing wall panels, andwith one of the beds of the curled separating media being provided foreach inlet. A common outlet may then be provided in the roof. The floormay be of V-shape in cross-section, tapering downwardly inwardly fromthe wall panels having the inlets and with the contaminant collectionzone being provided at or along the apex of the floor.

Gas/vapour deflection surface(s) may be provided opposite the inlet(s)for deflecting gas or vapour downwardly towards the bed(s). Thedeflection surface(s) may be curved. In the first version of theinvention, the deflection surface may be provided by the roof panel anda portion of that wall panel in which the outlet is located. In thesecond version of the invention, the deflection surfaces may be providedby additional panels spaced from the wall panels in which the inlets arelocated, and the roof panel.

The inlet(s) may extend the full length of the wall panel(s), while theoutlet may likewise extend the full length of the wall panel or theroof.

In yet another embodiment of the invention, the inlet may lead into thevessel at a high level, with the outlet being located centrally so thatthe bed of curled separating media is located around the outlet.

The wall may then be cylindrical. In particular, the wall may then becircular in cross-section so that the floor is circular in plan view.The floor may be of concave-shape or dish-shape curving downwardly andinwardly from the cylindrical wall to a lowermost centre point.

The outlet may comprise a cylindrical, eg circular in cross-section,component located centrally within the vessel such that a lower end ofthe component is spaced with clearance from the floor, and an upper endthereof protrudes beyond the upper end of the wall. A circumferentialflange may protrude radially outwardly from the upper end, or an upperend portion, of the cylindrical component. In use, the flange can beused to attach the apparatus to a ceiling, cooking hood, or the like.Circumferentially spaced connecting means, eg brackets, may thus connectthe cylindrical component to the wall.

The inlet may thus be defined between the flange and the upper end ofthe wall. Thus, the inlet will extend peripherally or circumferentiallyaround the vessel.

The flange and upper end portion of the cylindrical component may beshaped to provide a gas or vapour deflecting surface for deflecting gasor vapour entering through the inlet downwardly towards the bed ofseparating media.

The bed of separating media is thus located between the wall andcylindrical component, and extends around the component. The bed is thenthus also of cylindrical form.

The apparatus may include cooling means for cooling a gas or vapourstream immediately before it passes into the bed of separating media.The apparatus may then include a gas/vapour chamber between the inletand the separating media bed.

The cooling means may be adapted to cool the gas or vapour streamdirectly. The cooling means may comprise a cooling gas/vapour inletleading into the gas/vapour chamber. The cooling gas/vapour inlet maycomprise a coolant gas/vapour opening in the vessel, and a displaceableclosure for controlling the quantity of coolant gas/vapour passingthrough the opening. Displacement means for the closure, such as anelectric motor and lead screw arrangement, may also be provided.

Instead, or additionally, the cooling means may comprise cooling liquidinjection means for injecting a cooling liquid, such as cooling water,into the gas/vapour chamber. The injection means may comprise aplurality of nozzles for spraying cooling liquid into the chamberimmediately above the media bed, the nozzles connected or connectable toa cooling liquid supply. The nozzles may be mounted to a suitablecomponent, eg a bar, adapted to traverse the media bed. Thus, the barmay be provided with displacement means, such as an electric motor andlead screw arrangement, to enable it to be displaced to-and-fro acrossthe media bed, eg on a continuous basis.

The separating media bed may be displaceable. Thus, the separating mediabed may have an entry zone or portion at or through which contaminatedgas/vapour enters the bed, and an exit zone or portion at or throughwhich clean gas/vapour leave the bed. The apparatus may include a holderholding the separating media, the holder having opposed openingsproviding the entry and exit zones, and the openings being covered withapertured separating media retaining means, such as mesh. The holder maybe displaceable about a rotational axis. The holder will thus be shapedto permit rotation thereof, and the vessel will have complementaryseating components to match the holder and ensure that contaminatedgas/vapour does not bypass the media bed.

The apparatus may include washing means for washing the separating mediabed after displacement thereof. The washing means may include a washingliquid holding vessel; dosing means for dosing a washing chemical intothe vessel; heating means for heating the washing liquid in the vessel;pump means for pumping hot chemically dosed washing liquid from thevessel through nozzles onto the separating media bed; collection meansfor collecting used washing liquid which has passed through theseparating media bed, with the pump means also adapted to recycle theused washing liquid to the nozzles. The nozzles may thus be the coolingliquid nozzles. Instead of the pump means being used to pump hot washingliquid from the vessel, the vessel can be located above the nozzles,with the hot washing liquid then gravitating through the nozzlesinitially. As described hereinbefore, the washing liquid may, inparticular, be water.

The thickness or depth of the separating media bed may be between 3 cmand 15 cm, typically between 5 cm and 12 cm. The curled separating mediamay each having a dimension or length of between 3 mm and 30 mm, eg 15mm to 20 mm. By `curled separating media` is meant separating mediacomprising strips shaped to have the form of at least a partial ringletor spiral.

In one embodiment of the invention, the curled separating media may bewood shavings. However, in another embodiment of the invention, they maybe metal shavings, eg aluminium or steel shavings.

The thickness of the shavings may be less than 1 mm and even less than0.5 mm, eg about 0.1 mm, while the widths of the shavings may be between1 mm and 10 mm, eg about 5 mm. The radius of curvature of the shavingsmay be between 2 mm and 15 mm, eg about 8 mm. The lengths of the metalstrips obtained by straightening the shavings may be between 30 mm and100 mm, eg between 40 mm and 60 mm. The shavings may thus be of spiralor ringlet form.

According to a third aspect of the invention, there is provided acooking installation, which comprises

cooking apparatus on which foodstuffs can be cooked;

air collection means above the cooking apparatus for collecting oil andfat laden air generated by the cooking of foodstuffs on the cookingapparatus;

an extraction conduit leading from the air collection means such that aninlet to the conduit is provided in the air collection means;

air extraction means in or associated with the extraction conduit, forextracting air from the space between the air collection means and thecooking apparatus into the extraction conduit; and

separating apparatus as hereinbefore described, mounted to the aircollection means such that the outlet of the separating apparatus is incommunication with the conduit inlet.

The cooking apparatus may, in particular, be adapted such thatfoodstuffs can be grilled thereon, eg by means of a gas flame.

The air collection means may comprise a hood or the like, while theconduit may be in the form of a duct. The extraction means may be anextraction fan mounted in the duct.

Apart from fat and oil laden air entering the separating apparatus, inuse, cold air will also be drawn in from underneath the hood, with thecold air serving to condense the fats and oils from a gaseous form at ahigh temperature, typically about 170° C. immediately above the cookingapparatus, to a liquid form at a lower temperature, typically betweenambient temperature and 100° C., eg 20° C.-70° C., at which temperatureall oils and fats are in liquid form and at which temperature efficientseparation thereof in the bed of curled separating media can beeffected.

The invention will now be described by way of example with reference tothe accompanying diagrammatic drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 shows a simplified flow diagram of a separation process accordingto the first aspect of the invention, and including separation apparatusaccording to a first embodiment of the second aspect of the invention;

FIG. 2 shows an enlarged sectional view of the separation apparatus ofFIG. 1;

FIG. 3 shows an enlarged plan view of the separation apparatus of FIG.1;

FIGS. 4(a), (b) and (c) show three-dimensional views of typical curledseparating media used in the separating apparatus of FIGS. 1 to 3, and 5to 15;

FIG. 5 shows a three-dimensional view of separating apparatus accordingto a second embodiment of the second aspect of the invention;

FIG. 6 shows a cross-sectional view of a cooking installationincorporating the separating apparatus of FIG. 5;

FIG. 7 shows a three-dimensional view of separating apparatus accordingto a third embodiment of the second aspect of the invention;

FIG. 8 shows a cross-sectional view of a cooking installationincorporating the separating apparatus of FIG. 7;

FIG. 9 shows a plan view of a separating apparatus in accordance with afourth embodiment of the second aspect of the invention;

FIG. 10 shows a cross-sectional view through X--X of the separatingapparatus of FIG. 9;

FIG. 11 shows a sectional view through XI--XI of separating apparatusaccording to a fifth embodiment of the second aspect of the invention,with some details omitted for clarity;

FIG. 12 shows a plan view of the separating apparatus of FIG. 11, withsome details omitted for clarity;

FIG. 13 shows a part cut-away end view of the separating apparatus ofFIG. 11;

FIG. 14 shows a part cut-away plan view of separating apparatusaccording to a sixth embodiment of the second aspect of the invention,with some details omitted for clarity; and

FIG. 15 shows a part cut-away side view of the separating apparatus ofFIG. 14, with some details omitted for clarity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 3, reference numeral 10 generally indicates aseparation process according to the invention.

The process 10 includes a cooker 12, which includes heating means (notshown) for heating or cooking foodstuffs. A hood 14 is located above thecooker 12. A conduit 16 leads from the hood 14, and is provided with anopen limb 18 closed off with a removable plate 20. The conduit 16 leadsinto the top of separation apparatus, generally indicated by referencenumeral 22. A conduit 24 leads from a side of the apparatus 22 to ascrubber 26, with a conduit 28 leading from the scrubber 26 to abiological filter 30. A conduit 32 leads from the biological filter 30to the suction side of a fan 34, with an air discharge conduit 36leading from the fan 34 to atmosphere.

The separation apparatus 22 comprises a square roof 38, a square floor40 spaced from the roof 38, and side walls 42, 44, 46 and 48 extendingbetween the floor and roof. The conduit 24 thus leads from the wall 42,while the wall 46 is slidably attached to the walls 44, 48 so that it isremovable, thereby providing access to a separation zone 50 providedinside the apparatus 22. A tray 52 is located on the floor 40, and isslidably removable from the separation zone 50 through the gap providedwhen the wall 46 is removed.

The apparatus 22 also includes a basket, generally indicated byreference number 54. The basket 54 has an apertured base 56, a top 58which is spaced with limited clearance from the roof 38 and which has anopening which is aligned with the conduit 16, and side walls 60. A fixedbed 62 of curled separating media 70 is located in the basket 54, on topof the apertured base or grid 56. The basket is removable, being locatedon supports 57 protruding from the walls 44, 48.

The curled separating media 70 are as hereinafter described withreference to FIG. 4.

A baffle 64 depends from the roof 38 and terminates with clearance fromthe floor 40. The baffle extends from the wall 44 to the wall 48.

In use, foodstuffs are cooked in the cooker 12. The foodstuffs releasehot fats or oils, which can be in the form of liquid droplets orvaporized, into the air space above the cooker as they are cooked. Thesefats and oils are entrained or drawn up with air which is sucked in, bymeans of the fan or blower 34, into the hood 14. The fat and oil ladenair passes along the conduit 16 and enters the separation apparatus 22in a downward direction, as indicated by arrow 66. The fat and oil ladenair thus passes along the conduit 16, and enters the top of theseparation zone 50. In view of the enlarged cross-sectional area of thebasket 54 as compared to that of the conduit 16, the velocity (V₁) ofthe air entering the basket and passing through the bed 62 drops. Theair, still moving in a downward direction, encounters the curledseparating media 70. The separating media 70, in view of their shape,provide contact surfaces against which the entrained fat and oil canimpinge and be collected. Once sufficient or excess oil and fat haveaccumulated on the media 70, the oil and fat drip downwardly from themedia 70 into the tray 52 under gravity. The substantially oil and fatfree air passes into and through the portion of the separation zone 50below the basket 54 at a still lower velocity (V₂). The air then passes,as indicated by arrow 68, into the space between the lower edge of thebaffle 64 and the conduit 24, at a higher velocity, and then exitsthrough the conduit 24 at a still higher velocity.

The separation apparatus 22 may be sized such that the following airvelocities are attained therein:

v₁ --0.5 to 1.5 m/sec

v₂ --0.3 to 0.8 m/sec

The substantially oil and fat free air then passes into the scrubber 26where ammonia is removed by scrubbing the air with water. The air thenpasses along the conduit 28 into the biological filter, where sulphurouscompounds, such as mercaptans are removed, before being discharged intothe air via the conduit 36.

EXAMPLE

The separation apparatus 22 was tested in a prototype installation,having the layout of the process 10.

In the prototype installation, the dimensions of the separationapparatus 22 were 40 cm×40 cm×40 cm. The size of the basket 54 was 30cm×30 cm×30 cm. The diameter of the conduit 16 was 200 mm, while that ofthe conduit 24 was 140 mm. Instead of metal shavings, oak curls orshavings, having a maximum dimension of between 3 mm and 15 mm were usedas curled separating media in the basket 54, and the depth of the bed 62of oak curls was 12 cm.

A mixture of hard white animal fat and cooking oil was, in a simulationof an industrial cooker 12, heated to a temperature of 180° C. Water wasadded to the hot mixture of oil and fat, and allowed to boil or cookoff. The ambient air temperature was 21° C. It was found that the outlettemperature of the cooker, ie the temperature of the air at the inlet tothe hood 14, after the air had entrained the oil and fat, was in theregion of 65° C. to 70° C.

The air velocities in the separation apparatus 22 were as follows:

V₁ --1.3 m/sec

V₂ --0.7 m/sec

It was found that only the bottom 3 cm of the 12 cm bed 62 of separatingmedia became totally saturated with oil, with the upper 9 cm remainingrelatively oil and fat free. Excess oil dripped into the tray 52. Visualinspection of the conduit 16, which was effected by removing the plate20, showed that the conduit wall was extremely dirty and contaminatedwith oil and fat. In contrast, visual inspection of the conduit 24showed it to be substantially clean, and oil and fat free. After 5 hoursof simulating an industrial cooking process as described above, theconduit 24 was still substantially dry with no traces of fat or oilhaving deposited on its sides, as evidenced by rubbing the sides with aclean tissue.

After the cooking process had been stopped, the heat still present inthe apparatus 22 enable substantially all the fat and oil to drip out ofthe separating media into the tray 52. After the apparatus had beenallowed to cool down to below 10° C., it was found that there was only apressure increase of 3.5 mm water column across the bed 62, as comparedto the pressure drop across the unused bed before the test started. Itwas also determined that only 600 g of fat and oil had been absorbedinto the wood curls.

As a variation of the test, 25% excess cool air was sucked in throughthe conduit 18. It was found that this decreased the temperature of theair in the conduit 24 by 15° C., without affecting the performance ofthe apparatus 22.

In a further test variation, after 5 hours of normal cooking asdescribed above, the apparatus 22 was cooled down and then flooded with2 liters of cold hard fat and 4 liters of oil which were introduceddirectly into the top of the bed of separating media. The airtemperature through the apparatus 22 was then slowly increased to 40° C.for 15 minutes, and thereafter allowed to cool down to 18° C. It wasfound that the weight of the fat and oil retained in the separatingmedia, and the pressure drop across the bed remained the same as above,indicating that the media had reached saturation point and that theadditional fats and oils were merely knocked out and collected in thetray 52.

The Applicant believes that the apparatus 22 provides an effective meansof removing fats and oils from air, such as oil and fat laden air froman industrial cooker.

Referring to FIGS. 4(a), (b) and (c), reference numeral 70 generallyindicates individual curled separating media used in the separatingapparatus of FIGS. 1 to 3 and 5 to 15.

Each curled separating medium 70 is in the form of a metal shaving 72having a length `L` of about 15 mm to about 25 mm. The shavings 72 eachhave a thickness of about 0.1 mm, a width of about 6 mm and, whenstraightened, a length of about 40 mm to about 60 mm. Naturally, thesedimensions will not be the same for all shavings in the bed, but willnormally vary from shaving to shaving. Thus, typically, the length `L`can vary between 5 mm and 25 mm while the width can vary between 2 mmand 8 mm. The straightened length can vary between 30 mm and 100 mm. Theradii of curvature of the loops of the shaving 72 are about 5 mm to 10mm, but can vary, typically between 2 mm and 15 mm. The shavings 72 arethus in the form of spirals or ringlets.

The metal shavings may be of aluminium or steel. Instead, however, theseparating media may be of wood, eg may be in the form of wood curls,such as oak curls. Still further, the separating media may instead by ofplastics material, ceramic, or the like.

Referring to FIGS. 5 and 6, reference numeral 100 generally indicatesseparation apparatus according to a second embodiment of the secondaspect of the invention.

The separation apparatus 100 includes a vessel, generally indicated byreference numeral 102, providing a separation zone, generally indicatedby reference numeral 104.

The vessel 102 comprises a roof 106 which is rectangular in plan viewand has therein an air outlet 108 extending along the full length of theroof. The vessel 102 also includes a V-shaped floor 110, with a pair ofspaced parallel wall panels 112, 114 located between the roof 106 andthe floor 110 such that the floor 110 tapers downwardly inwardly fromthe wall panels 112, 114. Thus, an apex 116 of the floor 110 extendsparallel to the air outlet 108 in the roof 106. An air inlet 118 isprovided in the wall panel 112 at a relatively high level adjacent theroof 106, with the air inlet 118 extending the full length of the wallpanel 112. A similar air inlet 120 is provided in the wall panel 114.

A fat/oil collection zone 122 is provided at the apex of the floor 110.

A bed 124 of the curled separating media 70 is associated with each ofthe air inlets 118, 120, with the beds 124 being located inside theseparation zone 104. Each bed 124 rests on a apertured support 128,which may be a piece of mesh or the like, while a further aperturedsupport 130 is located on top of the beds 124 to hold the curledseparating media 70 in position. Typically, the beds 124 are about 12 cmdeep, but can be shallower if desired, eg about 5 cm deep.

The beds 124 are located between the wall panels 112, 114 and innerpanels 132 depending downwardly from the roof 106. The roof 106 andpanels 132 are arranged such that they provide curved air deflectingsurfaces 134 which serve to deflect entering through the air inlets 118,120 downwardly through the beds 124.

The vessel 102 also comprises end panels 136, 138 closing off therespective ends of the roof 106, walls 112, 114 and floor 110. An oildrainage tube 140 protrudes from the end panel 136 and is provided witha stopcock 142. The tube 140 is thus in communication with the zone 122,and oil and fat which has collected in the zone 122 can be drainedtherefrom through the tube 140.

In use, the separating apparatus 100 is used with a cooking hood 144which is located with clearance over a cooking apparatus 146, such as agas fired stove. The roof 106 of the separating apparatus 100 isattached to the hood 144 such that the air outlet 108 is locatedopposite the inlet to a duct 148 leading from the hood. An extractionfan 150 is located in the duct 148.

As foodstuffs, such as bits of chicken (not shown) are grilled on thestove 146, oil and fat laden hot air is generated above the stove 146.The hot air rises upwardly, assisted by the suction generated by theextraction fan 150. The hot fat and oil laden air, which is typically ata temperature of about 170° C. immediately above the stove 146, iscooled as it passes upwardly from the stove 146 to the separatingapparatus 100 since it is mixed with cold air drawn in underneath thehood. Thus, the air is cooled down to a temperature typically in theregion of 30° C.-40° C. by the time it enters the air inlets 118, 120 ofthe separating apparatus 100. The air then passes downwardly through thebeds 124 where, due to the curved surfaces of the separating media 70,the reduction of the air speeds and the reduction in temperature, thefats and oils are separated from the air. The fats and oils collect onthe curved surfaces of the media, and are then blown down into thecollection zone 122 from where they can periodically be removed by meansof the tube 140 and stopcock 142.

The curved surfaces 134 serve to deflect the air into the beds 124,thereby enhancing separation efficiency.

Cleaned air leaving the bottom of the beds 124 passes upwardly betweenthe space between the plates 132 into the duct 148 from where it isdischarged.

The various components of the apparatus are sized such that the velocityat which the fat and oil laden air enters the inlets 118, 120 is in theregion of 4 m/sec. The air velocity immediately decreases, and the airpasses through the beds 124 at a velocity of about 2.5 m/sec. Thedimension of the gap between the plates 132 is such that the velocity,V₂, of the air passing therethrough is in the region of 1 m/sec or less.

The Applicant has found that, apart from the beds 124 serving toseparate fats and oils efficiently from the air, they also act as flamearresters, with flames which enter the inlets 118, 120, eg as couldhappen if an abnormal situation occurs while using the stove 146, beingarrested by the beds 124 and hindered from reaching the zone 122. TheApplicant has also found that the separating media 70 are essentiallyself-cleaning since all oil and fat which collect thereon are forceddownward by gravity and the air flow into the zone 122 with no cleaningof the media being required. This is evidenced by the fact that, evenafter prolonged operation, tests have indicated that the pressure dropthrough the beds 124 remains consistently low, typically at a value ofabout 1.5 mm water gauge, indicating that there is no build-up of oilsor fats on the separating media.

Referring to FIGS. 7 and 8, reference numeral 200 generally indicatesseparation apparatus according to a third embodiment of the secondaspect of the invention.

Parts of the apparatus 200 which are the same or similar to theapparatus 100 shown in FIGS. 5 and 6, are indicated with the samereference numerals.

The apparatus 200 is similar to the apparatus 100, save that only asingle bed 124 of separating media is provided. Thus, only the air inlet118 is provided with no air inlet being provided in the wall panel 114.Instead, however, the air outlet 108 is provided in the wall panel 114.

The separating apparatus 200 functions in substantially the same fashionas the separating apparatus 100.

In FIGS. 9 and 10, reference numeral 300 generally indicates separationapparatus according to a fourth embodiment of the second aspect of theinvention.

The separation apparatus 300 includes a cylindrical vessel, generallyindicated by reference numeral 302, providing a separation zone 304.

The vessel 302 includes a concave-shaped or dish-shaped floor 310, witha cylindrical wall 312 protruding upwardly therefrom. The wall 312 iscircular in cross-section.

A cylindrical component 314 is located centrally within the vessel 302such that its lower end is spaced from the floor 310, while its upperend protrudes beyond the upper end of the wall 312. A circumferentialflange 306 protrudes outwardly from the upper end of the component 314.The component 314 thus provides a central circular air outlet 308.

The wall 312 is thus, in essence, an outer wall, while the component 314constitutes an inner wall.

The inner wall 314 typically has a diameter "D₁ ", of about 300 mm andthe outer wall 312 typically has a diameter "D₂ " of about 500 mm. Theouter and inner walls 312, 314 typically have a wall thickness ofapproximately 0.7 mm.

Brackets 315 are provided to space and connect the outer wall 312 to theinner wall 314 as shown in FIG. 10.

The floor 310 thus curves downwardly inwardly from the outer wall 312towards a lowermost centre point 316 of the floor 310 as shown, In otherwords, the centre point 316 of the floor 310 is at the lowermost pointof the vessel 302 in use. A fat/oil collection zone 322 is providedadjacent the floor 310. The vessel 302 also includes an oil drainagepipe 340 protruding from the centre point 316 of the floor 310 with theoil drainage pipe 340 being provided with a stopcock 342.

A circumferentially extending air inlet 318 is provided between theupper end of the outer wall 312 and the flange 306.

A cylindrical bed 324 of the curled separating media 70 is locatedinside the separating zone 304 and extends circumferentially around theinner wall 314 between the inner wall 314 and the outer wall 312 asillustrated. The bed 324 rests on an annular apertured support 328, eg apiece of mesh or the like, while a further annular apertured support 330is located on top of the bed 324 to hold the curled separating media 70in position. Typically, the bed 324 is about 12 cm deep.

The flange 306 and the inner wall 314 are arranged at right angles toeach other such that they provide air deflecting surfaces 334 whichserve to deflect air entering through the air inlet 318 downwardlythrough the bed 324.

In use, the separating apparatus 300 is used with a cooking hood 344which is located with clearance over a cooking apparatus 346, such as agas fired stove. The flange 306 of the separating apparatus 300 isattached to the hood 344 such that the air outlet 308 is locatedopposite an inlet of a duct 348 leading from the hood 344. An extractionfan 350 is located in the duct 348.

The apparatus 300 functions in substantially the same manner as theapparatus 100, 200.

Referring to FIGS. 11 to 13, reference numeral 400 generally indicatesseparating apparatus according to a fifth embodiment of the secondaspect of the invention.

The separating apparatus 400 includes a chamber, generally indicated byreference numeral 402. The chamber comprises a rectangular base 404 andsides 406, 408, 410 and 412 protruding upwardly from the base 404. Thesides 406, 410 are opposed to each other, while the sides 408, 412 areopposed to each other.

The chamber 402 houses a vessel, generally indicated by referencenumeral 414, providing an enclosed separation zone 416. The vessel 414comprises a rectangular base 418, a front wall 420, a rear wall 422, andopposed side walls 424, 426. A roof 428 closes off the upper ends of thewalls 420, 422, 424 and 426.

A contaminated air inlet, generally indicated by reference numeral 430,is provided in the front wall 420 of the vessel 414, with an air duct432 connected to the inlet 430.

An air outlet 434 is provided in the side wall or panel 426, with aconduit 436 leading from around the air outlet 434 to air dischargeducting 438, fitted with an electrically operable ventilator orextraction fan 439.

Partitioning 440 is provided inside the separation zone 416 so that anair chamber 442 is defined adjacent the air inlet 430. An atmospheric orcoolant air inlet 444 is provided in the roof 428, within the airchamber 442, so as to permit atmospheric or coolant air to enter the airchamber 412. A closure in the form of a pivotal flap 446 is provided,for regulating the effective size of the inlet or opening 444, and hencethe volume of coolant air which passes therethrough. The positioning ofthe flap 446 is controlled or regulated by means of an electricmotor/lead screw arrangement 448.

A bed 450 of the curled separating media 70 is provided below the airchamber 442 such that all air entering the air chamber 442 has to passdownwardly through the bed 450. The bed 450 is sandwiched between meshes452 which hold the separating media 70 in place.

The relative dimensions of the air inlet 430 and the air chamber 442 aresuch that the reduction in the air velocity as the air enters the airchamber, takes place. The air velocity, V₁, through the bed 450 can thusbe between 2 and 10 m/s, while the air velocity (V₂) in the separationzone 416 below the bed is less than 2 m/s. The thickness or depth of thebed 450 is typically in the range 5 cm to 12 cm.

An oil outlet or drain is provided in the floor 418, with a drainagepipe 454 leading therefrom.

The apparatus 400 also includes washing means, generally indicated byreference numeral 460, for washing the bed 450 of curled separatingmedia. The washing means 460 includes a water vessel or tank 462; awashing chemical, eg detergent, holding tank 464 connected to the tank462 by means of a conduit 466; an electrically operable heating element468 inside the tank 462; a cold water conduit 470 leading into the tank462; and a discharge conduit 472 leading from the bottom of the tank462. The conduit 472 leads to spray nozzles (not shown) located abovethe bed 450. A conduit 474 leads from the drain conduit 454 to thesuction side of a pump 476, with a conduit 478, fitted with anelectrically operable heater 480, leading from the pump discharge to theconduit 472.

Suitable valves (not shown) are provided in the various conduits foreffecting the washing operation as hereinafter described. These valves,as well as the electric motor 448 and the pump 476 may be linked to anautomatic controller, eg an electronic processor, so that operation ofthe apparatus 400 is effected automatically.

In use, hot air contaminated with undesired condensible vaporized fatand oil, such as that emanating from an industrial cooker, eg a potatochips cooker, enters the air chamber 442 through the air ducting 432.This air stream is typically at a temperature of about 87° C. This airis admixed with cooler atmospheric or coolant air entering through theinlet 444 and regulated to have a temperature of about 41° C. at whichthe fat and oil are in condensed, ie liquid, form. The flap 446 can beused to regulate the amount of cooler atmospheric or coolant airentering the air chamber 442.

The cooler mixed air stream thus formed passes downwardly through thebed 450 of curled separating media, with the curled separating mediaserving to remove fats and oils from the air. Purified air passesthrough the bottom of the bed, into the separating chamber 416 and outthrough the air outlet 434 to be discharged through the air ducting 438.

Fats and oils drip from the bottom of the bed 450, run along the floor418 and are discharged through the drain pipe 454.

Periodically, eg when the pressure drop through the bed 60 becomesexcessive, eg greater than 50 kPa, or otherwise merely on a regularbasis, when there is sufficient oil and fat build-up on the separatingmedia, a washing cycle using the washing means 460 is activated. Thiscan be effected automatically by suitable pressure differential controlmeans (not shown) or other control means. On actuation, cold waterenters the water tank 460 through the conduit 470. Sufficient detergentor other washing chemical is transferred from the vessel 464 into thetank 462. Thereafter the tank 462 is heated to a desired temperature atwhich efficient washing of the media can take place. The hot detergentcontaining water gravitates from the tank 462 through the washingnozzles, thereby being sprayed onto the bed 450. The water washes thebed 450 as it passes through it, and the contaminated water is collectedon the floor 418. The water flows to the oil discharge point and, bymeans of valves in the conduits 454, 474, is then recirculated by meansof the conduit 474, the pump 476 and the conduit 478, with the waterbeing reheated in the heater 480. Once the water has been recycled inthis fashion for a desired length of time to complete a washing cycle,the pump 476 is deactivated and the water discharged through the drainpipe 454.

It will be appreciated that while the washing cycle is taking place,contaminated air continues to pass through the bed 450 at the same time.

Referring to FIGS. 14 and 15, reference numeral 500 generally indicatesseparating apparatus according to a sixth embodiment of the secondaspect of the invention.

Parts of the apparatus 500 which are the same or similar to those of theapparatus 400 hereinbefore described with reference to FIGS. 11 to 13,are indicated with the same reference numerals.

While this is not shown, it is to be appreciated that the apparatus 500also includes washing means 460, as hereinbefore described.

In the apparatus 500, the spray nozzles for spraying the hot water ontothe bed of separating media are mounted to a transverse spray bar 502which is displaceable across the bed of separating media by means of anelectric motor and lead screw arrangement 504.

In the apparatus 500, the bed 450 is contained within a holder,generally indicated by reference numeral 506. The holder 506 comprisesend plates 508, and opposed side plates 510 extending between the endplates such that opposed openings 512 are provided between the sideplates 510. The side plates 510 are curved. The bed 450 is thuscontained between the end plates 508 and the side plates 510 and areretained in position by pieces of mesh 514 which span the openings 512.The holder 506 is provided with an axle 516, connected to an electricmotor 518 to permit rotation of the holder 514 through 180° so thateither of the openings 512 can be upwardly directed.

The vessel 414 includes components 519 having seats which arecomplementary to the sides 510 of the holder 514. This is to ensure thatcontaminated air does not bypass the bed contained in the holder 514.

In use, the apparatus 500 functions in similar fashion to the apparatus400 hereinbefore described. However, the apparatus 500 can be used witha contaminated air stream also containing solid matter to be removedtherefrom. This solid matter is thus also trapped in the bed 450. Whenthe pressure drop across the bed 450 is sufficiently high, eg greaterthan 50 kPa, it is automatically rotated through 180° so that the upperportion of the bed which is contaminated with solid matter, is thenlocated at the bottom. The force of the air passing through the bed willthen assist in dislodging the solid matter which will thus also collecton the floor 418. Additionally, the pulse of air which the upper side ofthe bed experiences as it is rotated, bearing in mind that while one ofthe side members 510 spans the air outlet of the air chamber, no flowthrough the bed takes place, also serves to dislodge solids in a shockfashion.

After the bed has been rotated through 180°, it is subjected to a washcycle, as hereinbefore described with reference to the apparatus 400.

It is to be appreciated that, in the apparatus 500, the nozzles mountedon the spray bar 502 can also be used to inject clean water into thespace above the bed during normal passage of air therethrough, to serveas additional cooling medium for cooling down the air. Typically, suchcooling water spray will be actuated once the flap 446 has been openedto its maximum so that the maximum amount of cooling air enters thechamber 52. Typically, when the flap 446 is about 55% open, the spray ofcooling water will be actuated.

During the wash cycle, the setting of the flap 446 can be controlled sothat the temperature of the air as it passes through the bed is somewhathigher than its normal operating temperature, eg about 60° C. ascompared to the normal operating temperature of about 41° C., to enhancecleaning of the separating media of the bed.

I claim:
 1. A separation process, which comprisespassing a gas or vapourstream contaminated with an undesired substance or contaminantdownwardly through a bed of curled separating media located in aseparation zone having a gas/vapour inlet and a gas/vapour outlet, withthe bed positioned between the inlet and the outlet such that thevelocity of the gas or vapour steam through the bed is lower than thevelocity of the gas or vapour steam through the gas/vapour inlet;allowing the undesired substance or contaminant to separate from the gasor vapour as it passes through the bed; withdrawing purified gas orvapour from the bed and allowing it to pass into and through a portionof the separation zone at a velocity which is lower than the velocity ofthe gas or vapour stream through the bed; allowing excess undesiredsubstance or contaminant to drip from the separating media; and catchingthis excess undesired substance or contaminant at the bottom of theseparation zone.
 2. A process according to claim 1, which includes, whenthe pressure drop through the media bed becomes excessive due tocontamination of the media and/or solids build-up in the bed, displacingthe bed so that the gas or vapour stream enters a different zone of thebed, the bed having an entry zone or portion through which thecontaminated gas or vapour stream enters the bed and an exit zone orportion through which the purified gas or vapour stream leaves the bed,with the zones being located on opposite sides of a rotational axis, andwith the displacement of the bed being through 180° and being effectedby rotating it about the axis so that the entry zone becomes the exitzone and the exit zone becomes the entry zone.
 3. A process according toclaim 1, wherein the contaminated gas or vapour stream is an off orwaste gas stream emanating from a household, commercial or industrialcooker, with the contaminant or undesired substance being fat and/oroil.
 4. A separation apparatus, which comprisesa vessel defining aseparation zone; a contaminated gas/vapour inlet leading into thevessel; a gas/vapour outlet leading from the vessel; separating meanscomprising a bed of curled separating media in the separation zone, theinlet, the separating means and the outlet arranged such that acontaminated gas or vapour stream entering the separation zone throughthe inlet passes downwardly through the bed, into and through a portionof the separation zone below the bed, and exits the zone through theoutlet, with the curled separating media acting to separate contaminantsfrom the gas or vapour as the gas or vapour stream passes through thebed, with the bed being of larger cross-sectional area than the inlet sothat the velocity of the gas or vapour stream through the bed is lowerthan the velocity of the gas or vapour stream through the gas/vapourinlet, and with the portion of the separation zone below the bed beingdimensioned so that the velocity of the gas or vapour through thatportion of the separation zone is lower than the velocity of the gas orvapour stream through the bed; and a contaminant collection zone insidethe vessel below the bed of curled separating media so that excesscontaminant can drip from the separating media and be caught in thecontaminant collection zone.
 5. An apparatus according to claim 4,wherein the vessel has a base or floor, a roof spaced from the base, anda peripheral wall between the base and the roof, with the inlet beingprovided in the roof, and the outlet being provided in the wall.
 6. Anapparatus according to claim 5, wherein the contaminant collection zoneis adjacent the floor such that it is spaced from the bed of curledseparating media, with the inlet being provided in the wall at a highlevel, and the outlet being provided in the wall and/or in the roof suchthat it is in communication with the space between the bed of curledseparating media and contaminant collection zone.
 7. An apparatusaccording to claim 6, wherein (i) the floor and roof is square orrectangular in plan view, with the wall thus comprising four wall panelsconnecting the floor and the roof, the inlet being provided in one wallpanel at said high level and the outlet being provided in an opposingwall panel at a lower level; or (ii) the floor and roof is square orrectangular in plan view, so that the wall comprises four wall panelsconnecting the floor and the roof, one of the inlets being provided ineach of two opposing wall panels, with one of the beds of the curledseparating media being provided for each inlet, and with a common outletbeing provided in the roof, the floor being of V-shape in cross-section,tapering downwardly inwardly from the wall panels having the inlets andwith the contaminant collection zone being provided at or along the apexof the floor.
 8. An apparatus according to claim 5, wherein thecontaminant collection zone is adjacent the floor such that it is spacedfrom the bed of curled separating media, with the inlet leading into thevessel at a high level, and with the outlet being located centrally sothat the bed of curled separating media is located around the outlet. 9.An apparatus according to claim 5, wherein the separating media bed isdisplaceable, the separating media bed having an entry zone or portionat or through which contaminated gas/vapour enters the bed, and an exitzone or portion at or through which clean gas/vapour leave the bed, withthe apparatus including a holder holding the separating media, theholder having opposed openings providing the entry and exit zones, theopenings being covered with apertured separating media retaining means.10. An apparatus according to claim 5, wherein the thickness of theseparating media bed is between 3 cm and 15 cm, with the curledseparating media each having a dimension or length of between 3 mm and30 mm.
 11. An apparatus according to claim 10, wherein the curledseparating media are metal shavings, the thickness of the shavings beingless than 1 mm while the widths of the shavings are between 1 mm and 10mm, the radius of curvature of the shavings being between 2 mm and 15mm, and the shavings being of spiral or ringlet form.